Moisture barrier film coating composition, method, and coated form

ABSTRACT

A dry moisture barrier film coating composition for forming a moisture barrier film coating for pharmaceutical tablets and the like comprises polyvinyl alcohol, soya lecithin, and optionally a flow aid, a colorant, and/or a suspending agent. A liquid coating solution or dispersion for forming a moisture barrier film coating for pharmaceutical tablets and the like comprises polyvinyl alcohol, soya lecithin, water, and optionally a flow aid, a colorant, and/or a suspending agent. A method of coating pharmaceutical tablets and the like with a moisture barrier film coating comprises forming a liquid coating solution or dispersion for forming a moisture barrier film coating for pharmaceutical tablets and the like comprising polyvinyl alcohol, soya lecithin, water, and optionally a flow aid, a colorant, and/or a suspending agent, applying the coating solution or dispersion onto the tablets to form a film coating on the tablets, and drying the film coating on the tablets.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is in the field of coating of substrates likepharmaceutical tablets, and it is specifically concerned with coatingsuch substrates with a coating that acts as a moisture barrier.

2. Description of the Prior Art

Many medicinal substances and the dosage forms into which they are madeundergo degradation during storage due to contact with moisture whichhas been absorbed from the atmosphere. To combat this degradation, it isfrequently necessary for such moisture sensitive dosage forms to bepacked in special containers to limit the exposure of the dosage formsto the atmosphere.

In territories where the climate is very humid, specialized packagingdoes not provide a totally satisfactory answer to moisture degradation.

Elimination of the need for the special packaging, or augmentation ofthe moisture protection provided by such packaging, may be achieved inthe case of solid dosage forms, such as tablets, capsules and granules,by coating with materials which reduce the rate at which the dosage formabsorbs atmospheric moisture. Moisture barrier coatings of this typehave been employed previously. The traditional means of providing themoisture barrier characteristics required for moisture barrier coatingshas been by the use of polymers which are soluble in organic solvents orare relatively insoluble in water. The disadvantages of this approachare 1) the need to use either organic solvents or difficult aqueouspolymer dispersion techniques to apply these water-insoluble polymermaterials, and 2) the reduced Aqueous solubility of the coating leadingto prolonged disintegration time of the dosage form in the body wheningested, with consequent delayed or reduced activity of the medicinalsubstance in the tablet.

The use of the polymer polyvinyl alcohol, PVA, as a moisture barriercoating has been previously suggested. However, practical usage has beeninhibited by the stickiness of grades of the polymer which have a fastenough rate of going into solution in water to make a dispersion torender them economical to use in making the coating. A further problemwith the use of PVA is in identifying or selecting a plasticizer whichdoes not compromise the moisture barrier properties of the finalcoating.

SUMMARY OF THE INVENTION

A dry powder moisture barrier coating composition is made to form amoisture barrier film coating for pharmaceutical tablets and the like,which comprises polyvinyl alcohol in combination with soya lecithin,together with, none, one or more of the following components whichenhances the desirable coating characteristics of the resulting filmcoating: a flow aid, a colorant, and a suspending agent.

A method of making the moisture barrier film coating powder compositionof the invention comprises the steps of mixing polyvinyl alcohol withsoya lecithin and optionally with one or more of the followingcomponents, until a dry homogenous powder mixture is produced: a flowaid, a colorant, and a suspending agent. Preferably, the mixture ofpolyvinyl alcohol and soya lecithin, or the mixture of polyvinyl alcoholand soya lecithin and any of the following components, if any of thefollowing components is to be included in the coating composition, ismilled: a flow aid, a colorant, and a suspending agent. The resultingdry powder coating composition is readily soluble or dispersible in coldwater to form a liquid coating solution or dispersion that is ready touse within 45 minutes.

Another method of making a dry edible film coating composition of theinvention comprises producing a mixture of the ingredients processedinto a granular form to form a granular coating composition by using anyof the following methods: wet massing, fluid bed granulation, spraygranulation and dry compaction, roller compaction or slugging.

The invention also includes a liquid coating solution or dispersion forforming a moisture barrier film coating which comprises polyvinylalcohol, soya lecithin, an optional flow aid, an optional colorant, andan optional suspending agent mixed into water.

The method of making the liquid coating dispersion of the inventioncomprises dispersing the dry powder coating composition, the granularcoating composition, or the individual ingredients of the coatingcomposition separately, into hot or cold water, and/or milling and/orstirring until a homogenous mixture of a desired correct viscosity isproduced.

The film former of the coating is the polyvinyl alcohol, which may beGOHSENOL polyvinyl alcohol made by NIPPON GOHSEI, for example.

Excellent moisture barrier properties are obtained when hot watersoluble grades of PVA are used in the inventive coating, but use of suchgrades requires that the water of the liquid coating dispersion beheated. The coatings of the invention may use cold water soluble gradesof PVA to provide moisture barrier protection, but they provide lessmoisture barrier protection than that provided by the inventive coatingsthat use hot water soluble grades of PVA. A preferred grade of PVA foruse in the inventive coating is a grade in the medium range (i.e., thegrades of PVA between the grades that dissolve only in hot water and thegrades that dissolve very easily in cold water) of PVA because the stepof heating the water of the liquid coating dispersion may not benecessary, while still maintaining excellent moisture barrier propertiesin the inventive coating.

The flow aid may be talc, fumed silica, lactose or starch.

The colorant may be any food approved colors, opacifiers, or dyes. Forexample, these may be aluminum lakes, iron oxides, titanium dioxide, ornatural colors.

The soya lecithin, which may be ALCOLEC soya lecithin made by AmericanLecithin Company, for example, acts an a anti-tack agent, andsurprisingly, and unexpectantly, acts as a plasticizer by lockingmoisture in the coating so the coating stays flexible and not brittle.Surprisingly and unexpectantly, this locked-in moisture in the coating,while contributing to plasticization, does not compromise the moisturebarrier properties of the overall coating.

The suspending agent acts as a viscosity modifier stabilizing thecoating dispersion. A preferred suspending agent is xanthan gum.Examples of alternative suitable suspending agents includehydroxypropylmethlycellulose (HPMC), alginates, hydroxypropyl cellulose(HPC), natural gums, and carboxymethylcellulose.

The ranges for each component of the dry coating compositions of theinvention are as follows, by weight:

    ______________________________________                Acceptable                          Preferred                Ranges    Ranges    ______________________________________    Polyvinyl Alcohol                  20.0% to 99.8%                                30 to 99.0%    Flow Aid       0.0% to 40.0%                              14.0 to 25.0%    Colorant       0.0% to 60.0%                              25.0 to 40.0%    Soya Lecithin  0.2% to 10.0%                              1.0 to 6.0%    Suspending Agent                  0.0% to 2.0%                              0.15 to 1.0%    ______________________________________

The ranges for each component of the liquid coating dispersions of theinvention are as follows, by weight:

    ______________________________________                Acceptable                          Preferred                Ranges    Ranges    ______________________________________    Polyvinyl Alcohol                   5.0 to 40.0%                               7.0 to 12.0%    Flow Aid       0.0 to 16.0%                              3.0 to 5.0%    Colorant       0.0 to 24.0%                              4.8 to 8.0%    Soya Lecithin 0.04 to 4.0%                              0.3 to 0.5%    Suspending Agent                  0.0 to 0.8% 0.07 to 0.12%    Water         60.0 to 95.0%                              75.0 to 85.0%    ______________________________________

DETAILED DESCRIPTION

We now turn to the examples of the invention, all ingredients being byweight.

EXAMPLE 1

455.2 grams of polyvinyl alcohol, 200.0 grams of talc, 320.0 grams oftitanium dioxide, 4.8 grams of xanthan gum, and 20.0 grams of soyalecithin are loaded into a dry powder mill, such as a PK blender, andvigorously mixed therein for 25 minutes or until a homogenous mix isachieved, resulting in one formulation of the inventive dry powdermoisture barrier film coating composition.

480 grams of this formulation of the inventive dry powder moisturebarrier film coating composition is dispersed in 1701.8 grams ofpurified water to form an aqueous suspension of the invention.Specifically, 1701.8 grams of purified water at ambient temperature isloaded into a vessel having a diameter that is approximately equal tothe depth of the final suspension. A low shear mixer, preferably havinga mixing head that has a diameter that is approximately 1/3 the diameterof the mixing vessel, is lowered into the water and turned on to createa vortex from the edge of the vessel down to just above the mixing headwithout any air being drawn into the water. Then, the 480.0 grams of themoisture barrier film coating powder composition is added to the vortexat a rate where there is no excessive build up of dry powder. The speedor depth of the mixing head is adjusted to avoid air being drawn intothe suspension so as to avoid foaming. The suspension is stirred for 45minutes and is then ready for spraying onto substrates likepharmaceutical tablets.

In this Example 1, 10 Kg of tablets are coated with the coating of theinvention so as to obtain about a 4.0% weight gain. The extra 80 gramsof the dry powder moisture barrier film coating composition above the400 grams of the dry powder moisture barrier film coating compositionneeded to obtain a 4.0% weight gain on the tablets is included to allowfor losses of coating composition during the coating procedure. 10 Kg oftablets which have logos embossed therein are loaded into a ManestyModel 10 Accela-Cota coater, and the tablets are rotated in the coaterat a rotation speed of 12 rpm. The tablets are sprayed with the coatingsuspension of this Example 1 while the tablets are being rotated. Hotair at 60° C. is used to evaporate the water in sprayed coatingsuspension and to maintain the tablets at 38° C.

Upon completion of the coating process, the tablets show a smoothsurface with excellent logo definition.

In the following Examples 2 to 14, one Kg batches of coating suspensionare produced by mixing 220 grams of inventive dry powder moisturebarrier coating composition into 780 grams of purified water. Thesecoating suspensions are then sprayed onto tablets. The procedures setout in Example 1 for making the dry powder moisture barrier coatingcomposition, for making the coating suspension, and for spraying thecoating suspension onto tablets are used in Examples 2 to 14. The coatedtablets of the Examples 2 to 14 show a smooth surface with excellentlogo definition.

EXAMPLE

    ______________________________________    COMPONENT       PERCENTAGE  GRAMS    ______________________________________    PVA             45.85       458.50    TALC            20.00       200.00    TITANIUM DIOXIDE                    32.00       320.00    XANTHAN GUM      0.15        1.50    SOYA LECITHIN    2.00       20.00                    100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT       PERCENTAGE  GRAMS    ______________________________________    PVA             44.80       448.00    TALC            20.00       200.00    TITANIUM DIOXIDE                    32.00       320.00    XANTHAN GUM      1.20       12.00    SOYA LECITHIN    2.00       20.00                    100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT       PERCENTAGE  GRAMS    ______________________________________    PVA             46.52       465.20    TALC            20.00       200.00    TITANIUM DIOXIDE                    32.00       320.00    XANTHAN GUM      0.48        4.80    SOYA LECITHIN    1.00       10.00                    100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT       PERCENTAGE  GRAMS    ______________________________________    PVA             41.52       415.20    TALC            20.00       200.00    TITANIUM DIOXIDE                    18.00       180.00    YELLOW IRON OXIDE                    14.00       140.00    XANTHAN GUM      0.48        4.80    SOYA LECITHIN    6.00       60.00                    100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT       PERCENTAGE  GRAMS    ______________________________________    PVA             31.64       316.40    TALC            34.09       340.90    TITANIUM DIOXIDE                    32.00       320.00    XANTHAN GUM      1.13       11.30    SOYA LECITHIN    1.14       11.40                    100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT       PERCENTAGE  GRAMS    ______________________________________    PVA             50.40       504.00    TALC            14.40       144.00    TITANIUM DIOXIDE                    32.00       320.00    XANTHAN GUM      1.20       10.00    SOYA LECITHIN    2.00       20.00                    100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT       PERCENTAGE  GRAMS    ______________________________________    PVA              99.00       990.00    SOYA LECITHIN    1.00        10.00                    100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT       PERCENTAGE  GRAMS    ______________________________________    PVA              99.80       998.00    SOYA LECITHIN    0.20         2.00                    100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT         PERCENTAGE  GRAMS    ______________________________________    PVA               44.00       440.00    TALC              20.00       200.00    TITANIUM DIOXIDE  18.00       180.00    TARTRAZINE ALUMINUM                      14.00       140.00    LAKE    XANTHAN GUM        2.00        20.00    SOYA LECITHIN      2.00        20.00                      100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT       PERCENTAGE  GRAMS    ______________________________________    PVA             50.80       508.00    TALC            14.00       140.00    TITANIUM DIOXIDE                    32.00       320.00    XANTHAN GUM      1.20        12.00    SOYA LECITHIN    2.00        20.00                    100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT       PERCENTAGE  GRAMS    ______________________________________    PVA             40.52       405.20    TALC            25.00       250.00    TITANIUM DIOXIDE                    32.00       320.00    XANTHAN GUM      0.48        4.80    SOYA LECITHIN    2.00        20.00                    100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT       PERCENTAGE  GRAMS    ______________________________________    PVA             25.52       255.20    TALC            40.00       400.00    TITANIUM DIOXIDE                    32.00       320.00    XANTHAN GUM      0.48        4.80    SOYA LECITHIN    2.00        20.00                    100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT       PERCENTAGE  GRAMS    ______________________________________    PVA             45.52       455.20    TALC            20.00       200.00    TITANIUM DIOXIDE                    32.00       320.00    XANTHAN GUM      0.48        4.80    SOYA LECITHIN    2.00        20.00                    100.00      1000.00    ______________________________________

EXAMPLE

    ______________________________________    COMPONENT        GRAMS    ______________________________________    WATER             1170.00    PVA               150.00    TALC               66.00    TITANIUM DIOXIDE  105.75    XANTHAN GUM        1.65    SOYA LECITHIN      6.60                      1500.00    ______________________________________

The coating dispersion of this Example 15 is made and used using theprocedures set out in Example 1.

It was unexpectedly found that soya lecithin, included for its tackreduction properties, acts as a plasticizer by locking moisture in thecoating so as to keep the coating flexible and not brittle. It is alsoconsidered unexpected that this moisture while contributing toplasticization, does not compromise the moisture barrier properties ofthe overall coating.

This invention provides the means of preparing a moisture barriercoating for application to pharmaceutical solid dosage forms in whichthe coating composition material is presented as a dry particle powderor granular powder which is readily dispersible in cold water. Theresultant coating solution or dispersion is ready to use by applying itto tablets within 45 minutes. The coating solution or dispersion mayalso be presented in the form of a ready-to-use liquid, or liquidconcentrate which is diluted prior to use.

Compared with existing moisture barrier coatings using water insolublepolymers, there is negligible effect on the disintegration time of thecoated dosage forms coated with the inventive coating.

The dry form of the invention is manufactured using rotary mixers ormills. The ingredients are loaded and then milled until a homogenous mixis produced. In the case of liquid dispersions, the ingredients aredispersed into hot or cold water and stirred or milled until ahomogenous dispersion or solution of the desired correct viscosity isproduced.

The dry form of the invention, which comprises a powder of PVA and soyalecithin, and optionally a flow aid, a colorant, and a suspending agent,is dispersed in water and stirred until the PVA is hydrated and ahomogenous mixture is produced. The liquid solution or dispersionformed, which comprises PVA, soya lecithin, and any optional componentsmixed into water, may be ready-to-use or require simple dilution withwater prior to use. The resulting coating dispersion is sprayed onto thedosage forms using airless or airborne methods. The movement of airaround or through the tablet bed facilitates drying of the film on thetablet surface.

I claim:
 1. A liquid moisture barrier film coating composition forforming a moisture barrier film coating for pharmaceutical tabletscomprisingpolyvinyl alcohol, soya lecithin, water, and a viscositymodifier, the viscosity modifier being xanthan gum,hydroxypropyl-methylcellulose, alginate, hydroxypropyl cellulose,natural gums, carboxymethylcellulose, or combinations thereof.
 2. Aliquid moisture barrier film coating composition for forming a moisturebarrier film coating for pharmaceutical tablets comprisingpolyvinylalcohol, soya lecithin, and water, the water being in a range of about60.0% to about 95.0% by weight of the composition.
 3. The liquidcomposition of claim 2,the water being in a range of about 75.0% toabout 85.0% by weight of the composition.
 4. A pharmaceutical tabletcoated with a moisture barrier film coating made using a dry moisturebarrier film coating composition for forming a moisture barrier filmcoating for pharmaceutical tablets comprising polyvinyl alcohol, a flowaid, a colorant, a viscosity modifier, and soya lecithin.
 5. A drymoisture barrier film coating composition for forming a moisture barrierfilm coating for pharmaceutical tablets comprisingpolyvinyl alcohol, andsoya lecithin the polyvinyl alcohol being in a range of about 20.0% toabout 99.8% by weight of the composition, and the soya lecithin being ina range of about 0.2% to about 10.0% by weight of the composition. 6.The coating composition of claim 5,the polyvinyl alcohol being in arange of about 30.0% to about 99.0% by weight of the composition, andthe soya lecithin being in a range of about 1.0% to about 6.0% by weightof the composition.
 7. A dry moisture barrier film coating compositionfor forming a moisture barrier film coating for pharmaceutical tabletscomprisingpolyvinyl alcohol, soya lecithin, and a flow aid the flow aidbeing in a range of greater than 0.0% to about 40.0% by weight of thecomposition.
 8. The composition of claim 7,the flow aid being in a rangeof about 14.0% to about 25% by weight of the composition.
 9. A drymoisture barrier film coating composition for forming a moisture barrierfilm coating for pharmaceutical tablets comprisingpolyvinyl alcohol,soya lecithin, and a flow aid, the flow aid being talc, fumed silica,lactose, or starch.
 10. A dry moisture barrier film coating compositionfor forming a moisture barrier film coating for pharmaceutical tabletscomprisingpolyvinyl alcohol, soya lecithin, and a colorant, the colorantbeing in a range of greater than 0.0% to about 60.0% by weight of thecomposition.
 11. The coating composition of claim 10,the colorant beingin a range of about 25.0% to about 40.0% by weight of the composition.12. A dry moisture barrier film coating composition for forming amoisture barrier film coating for pharmaceutical tabletscomprisingpolyvinyl alcohol, soya lecithin, and a colorant, the colorantbeing any food approved colors, opacifiers or dyes.
 13. A dry moisturebarrier film coating composition for forming a moisture barrier filmcoating for pharmaceutical tablets comprisingpolyvinyl alcohol, soyalecithin, and a viscosity modifier, the viscosity modifier being in arange of greater than 0.0% to about 2.0% by weight of the composition.14. The coating composition of claim 13,the viscosity modifier being ina range of about 0.15% to about 1.0% by weight of the composition.
 15. Adry moisture barrier film coating composition for forming a moisturebarrier film coating for pharmaceutical tablets comprisingpolyvinylalcohol, soya lecithin, and a viscosity modifier, the viscosity modifierbeing a xanthan gum.
 16. A dry moisture barrier film coating compositionfor forming a moisture barrier film coating for pharmaceutical tabletscomprisingpolyvinyl alcohol, soya lecithin, and a viscosity modifier,the viscosity modifier being hydroxypropyl-methylcellulose, alginate,hydroxypropyl cellulose, natural gums, carboxymethylcellulose, orcombinations thereof.
 17. The coating composition of claim 6,the soyalecithin being in a range of about 1.0% further including a flow aid,the flow aid being in a range of about 14% to about 25% by weight of thecomposition, the flow aid being talc, fumed silica, lactose, or starch,a colorant, the colorant being in a range of about 25.0% to about 40.0%by weight of the composition, the colorant being any food approvedcolors, opacifiers, or dyes, a viscosity modifier, the viscositymodifier being in a range of about 0.15% to about 1.0% by weight of thecomposition, the viscosity modifier being xanthan gum,hydroxypropyl-methylcellulose, alginate, hydroxypropyl cellulose,natural gums, carboxymethylcellulose, or combinations thereof.
 18. Amethod of coating substrates with a moisture barrier film coating,comprisingmixing the coating composition according to claim 5 into waterto form an aqueous coating solution/dispersion, applying the coatingsolution/suspension onto the substrates to form a film coating on thesubstrates, and drying the film coating on said substrates.
 19. Apharmaceutical tablet coated with a moisture barrier film coating madeusing the coating composition according to claim
 17. 20. A method ofcoating substrates with a moisture barrier film coating,comprisingmixing the coating composition according to claim 17 intowater to form an aqueous coating solution/dispersion, applying thecoating solution/suspension onto the substrates to form a film coatingon the substrates, and drying the film coating on said substrates.
 21. Adry moisture barrier film coating composition for forming a moisturebarrier film coating for pharmaceutical tablets comprisingpolyvinylalcohol, and soya lecithin, the polyvinyl alcohol being in a range ofabout 20.0% to about 99.8% by weight of the composition.
 22. A drymoisture barrier film coating composition for forming a moisture barrierfilm coating for pharmaceutical tablets comprisingpolyvinyl alcohol, andsoya lecithin, the soya lecithin being in a range of about 0.2% to about10.0% by weight of the composition.
 23. A coated substrate made inaccordance with the method of claim
 18. 24. A liquid moisture barrierfilm coating composition for forming a moisture barrier film coating forpharmaceutical tablets comprisingpolyvinyl alcohol, soya lecithin, andwater, the polyvinyl alcohol being in a range of about 5.0% to about40.0% by weight of the composition, and the soya lecithin being in arange of about 0.04% to about 4.0% by weight of the composition.
 25. Theliquid composition of claim 24,the polyvinyl alcohol being in a range ofabout 7.0% to about 12.0% by weight of the composition, and the soyalecithin being in a range of about 0.3% to about 0.5% by weight of thecomposition.
 26. A liquid moisture barrier film coating composition forforming a moisture barrier film coating for pharmaceutical tabletscomprisingpolyvinyl alcohol, soya lecithin, water, and a flow aid, theflow aid being in a range of greater than 0.0% to about 16.0% by weightof the composition.
 27. The liquid composition of claim 26,the flow aidbeing in a range of about 3.0% to about 5.0% by weight of thecomposition.
 28. A liquid moisture barrier film coating composition forforming a moisture barrier film coating for pharmaceutical tabletscomprisingpolyvinyl alcohol, soya lecithin, water, and a flow aid, theflow aid being talc, fumed silica, lactose, or starch.
 29. A liquidmoisture barrier film coating composition for forming a moisture barrierfilm coating for pharmaceutical tablets comprisingpolyvinyl alcohol,soya lecithin, water, and a colorant, the colorant being in a range ofgreater than 0.0% to about 24.0% by weight of the composition.
 30. Theliquid composition of claim 29,the colorant being in a range of about4.8% to about 8.0% by weight of the composition.
 31. A liquid moisturebarrier film coating composition for forming a moisture barrier filmcoating for pharmaceutical tablets comprisingpolyvinyl alcohol, soyalecithin, water, and a colorant, the colorant being any food approvedcolors, opacifiers or dyes.
 32. A liquid moisture barrier film coatingcomposition for forming a moisture barrier film coating forpharmaceutical tablets comprisingpolyvinyl alcohol, soya lecithin,water, and a viscosity modifier, the viscosity modifier being in a rangeof greater than 0.0% to about 0.8% by weight of the composition.
 33. Theliquid composition of claim 32,the viscosity modifier being in a rangeof about 0.07% to about 0.12% by weight of the composition.